Abstract: A thermally compensated circuit breaker has a movable contact assembly (24) which mounts a movable electrical contact (24m) for movement between open and closed contacts positions with a stationary electrical contact (26). The contacts are maintained in the closed circuits position by a latching mechanism (24b, 28g) which prevents opening of the contacts through an opening contacts force provided by a spring (24e). A current carrying trip arm (40a, 44a) deflects upon sufficient I2R heating to transfer motion to the latch to separate the latch (24b) from the latch receiving catch (28g) to trip the circuit breaker. The trip arm (40a, 44a) is part of a pivotably mounted actuator assembly (40, 44) having a movable end portion spaced from the pivot disposed adjacent a motion transfer member (28c). A calibration screw (42a) is located so that the longitudinal axis is in line with a movable end portion of the actuator assembly and the motion transfer member.

Abstract: An electric circuit breaker (10) has a toggle mechanism (18) having two movable over center joints (3, 4) connected between a push-button (16) and a movable contact mechanism (30). When the push-button is depressed a first link rotates bringing the first movable over center joint (3) across a center position represented by a first imaginary straight line (1) to a stop surface (28). A spring member (36) provides a bias which acts on the second movable over center joint (4) normally maintaining the second movable joint against the stop surface so that with the two movable over center joints biased against the stop surface the movable contact mechanism is moved to a closed contact position when the push-button is depressed.